1. Field of the Invention
This invention relates to a method for the extraction of gold and silver from ore. More particularly, this invention relates to a method for extracting gold and silver into an organic solvent from ore, which method is characterized by causing the ore to contact an elemental halogen, a halogenated salt, and an organic solvent.
2. Prior Art Statement
Numerous methods have been proposed to date for extraction of gold and silver into a solution from an ore containing gold and silver. Among these conventional methods, the cyanide method excels in operational efficiency and economy and has found the most extensive utility. This method comprises bringing pulverized ore into contact with air in an aqueous solution of calcium cyanide (or potassium cyanide or sodium cyanide) thereby oxidizing gold and silver and converting the gold and silver into a water-soluble cyan complex and extracting the cyan complex ("Science of Noble Metals, Fundamentals", page 364, compiled by Taira Suzuki and Kenjiro Meguro and published by Tanaka Kikinzoku K. K.).
The cyanide method has the disadvantage that the operation thereof is highly dangerous because it requires use of a large amount of a highly poisonous cyan compound and the step of extraction consumes a long time because the oxidation reaction of gold and silver with the oxygen in the air progresses slowly.
The present inventors conducted a study in search of a method for safe and highly efficient extraction of gold and silver through which they found that gold and silver contained in an ore are readily dissolved in an organic solvent containing an elemental halogen and a halogenated salt. The present invention has been completed as a result.